Detailed modelling and simulation of UPFC using EMTP

This paper describes the modelling and simulating techniques for a multi-pulse based unified power flow controller (UPFC) using the Electromagnetic Transients Program (EMTP) simulation package. The UPFC consists of two voltage source inverters operated from a common dc linked capacitor, and composed of forced commutated power semiconductor switches. The two voltage source inverters are used to control the active and reactive power in the transmission line by injecting variable voltage in series and reactive current in shunt. The internal structure and regulation method for each voltage source inverter have been fully studied. We also proposed a control strategy for UPFC in which we control power flow through the line and maintain the transmission line voltage to a reference value at the point of connecting. The static and dynamic characteristics of UPFC are studied with the proposed model connected to a simplified power system. The simulation results clearly illustrate the feasibility of the modelling techniques adopted including the effectiveness of UPFC.